Avalanche Forecast

You can still trigger Wind Slabs at upper elevations near Mt Baker and the West North zone. Wind drifted snow over a weak layer as recent as Wednesday. Steer around recent drifts and deeper pillows of snow on steep wind exposed slopes to keep from triggering these avalanches.

Warm temperatures and sun on Saturday will make it easier to trigger wet avalanches, especially in areas where they haven't recently run. Loose Wet avalanches may occur at higher elevations or on more shaded aspects (facing west, north, and east). While Loose Wet avalanches are often smaller and easier to predict, they can be dangerous in high consequence terrain. Avoid extreme terrain or areas where getting caught in a wet avalanche would be especially dangerous. This includes steep slopes above rocks and cliffs, tight gullies, or trees.

Minimal freeze Friday night raises concern for other warming and wet snow related avalanches. Watch out for snow-covered rock slabs at mid to lower elevations and slopes with exposed cracks where Glide avalanches could occur. Avoid any known locations (especially near Snoqualmie Pass and the Mt Baker backcountry) that are notorious for producing Glide avalanches. Cornices have built in the past week. They typically fall during warming periods like what we will experience on Saturday. Whether your walking on a ridge or traveling on slopes, give cornices plenty of room. Wet Slabs are very difficult to predict and can be very large and destructive. Avoid avalanche terrain, if you find slopes with unsupportive, wet snow or where a known weak layer is getting wet.

You can still trigger Wind Slabs in the northern Cascades near Mt Baker. These drifted slabs lay over a thin layer that is taking longer to heal. Meanwhile to the south, it is now difficult to trigger Wind Slabs.

Warm air temperatures, light rain, and sun over the last several days created moist to wet surface snow in many locations. Generally, two or more feet of melt-form snow exists at the snow surface. Wet surface snow resulted in a loose wet avalanche cycle in the Snoqualmie Pass area. This likely occurred in other locations as well.

At higher elevations drier soft snow can still be found. The elevation where this transition occurs can vary even with in a zone. Typically drier snow can be found above 6500 feet in the southern areas an near 5000 feet in the northern areas. Moderate winds formed wind slabs as recent as Wednesday near and above treeline. Wind Slab avalanches are now hard to trigger.

Several avalanches 3/24-3/27 in the Crystal and Stevens areas failed on a layer of weak older snow buried on 3/22. Observations this week demonstrate this layer has been gaining strength. In some locations you may find a layer of small sugary facets above a firm melt-freeze crust. This layer has generally been reported 12-20” (30-50cm) below the snow surface and may be most prevalent above 5,500ft.

The much older 2/13 facets layer just above the 2/8 melt-freeze layer can still be found 4-6 feet (120-200cm) deep in the snowpack. While neither of these layers are listed in our current avalanche problem set, they may reawaken if they become wet.

Observations

North

On Friday, NWAC Observers Lee Lazara and Simon Trautman traveled in the Bagley Lakes area. They reported 3 triggered or natural avalanches about 1 foot deep on north aspects near treeline on slopes with recently drifted snow. The observers found a thin weak layer buried 3/25 at the interface of concern.

On Wednesday Mt Baker Ski Patrol reported 8-12 inches (20-30cm) of soft snow over a recent melt-freeze crust. This snow was very rapidly effected by small sun breaks and thinning in the clouds. Winds earlier in the weak formed new wind slabs at higher elevations.